THE first thing you should know about Harlem Week is that it isn’t a week. More like a month . . . and a few days.

And that is a paradox that will never be resolved.

“That’s become one of the most-asked questions of Harlem Week,” says chairman Lloyd Williams. “We chose to never change that because it always stimulates discussion.”

What began as Harlem Day in 1974 is now a major summer happening. A few warm-up events – like last Saturday’s Harlem Book Fair or the Empire State Building lights shining red, black and green since Wednesday – have been building up to Sunday’s kickoff, “A Great Day in Harlem.”

Starting at 1 p.m., the free event begins with Broadway and off-Broadway performances, followed by a fashion show of local designers, and ending with “What’s Going On,” a musical tribute to the music of Marvin Gaye.

That’s just Day One, people.

Even Harlem Day proper can’t be contained to a single day. This year it’s being celebrated on Saturday, Aug. 19, and Sunday, Aug. 20, with a weekendlong block party along 135th Street.

“It’s a heck of a lot more than a block party,” Williams insists. “It brings people to museums, churches, art galleries, boutiques, sporting events – last year it attracted 3.2 million people to 107 events.”

This year, it’s gone one better, with 108.

“We tried to reduce the number of events so you can focus better,” Williams explains, “but there are always new and creative things that are excellent ideas.”

We’ve highlighted some of them below, but go to harlemweek.harlemdiscover.com for the complete schedule.

In honor of Harlem Week, the Signature Theater presents August Wilson’s play. Through Sept. 24. The Signature Theatre, 555 W. 42nd St. For a $15 Harlem Week ticket price, use the code “GHCC” when contacting the box office at (212) 244-7529, signaturetheatre.org

Wednesday to Aug. 5: “Hollywood in Harlem”

Ebony magazine presents a mini film festival with Steve Harvey’s new film, “Steve Harvey: Don’t Trip . . . He Ain’t Through With Me Yet,” “Color of the Cross,” “Dirty Laundry,” “Half-Nelson” and “The Cheetah Girls 2.” Harvey and cast members from the other films will be at the screenings. For a schedule, visit ebonymagazine.com/assembled/events.html

Aug. 18 to Aug. 20: Tri-State Jr. Tennis Classic

Get ready for the U.S. Open with the best boys and girls in age divisions from 12 through 18. 1 p.m. to 7 p.m. Fred Johnson Tennis Courts, 150th Street and Adam Clayton Powell Jr. Boulevard; free.

Aug. 19: Harlem Day

The musical theme to “Uptown Saturday Nite” is “Jammin,’ ” and that’s what they’ll be doing on West 135th Street from Malcolm X Boulevard to St. Nicholas Avenue, from 11 a.m. to 8 p.m.; free; rain date: Aug. 26

Aug. 20: Harlem Day

This is what we’ve all been working towards. The theme is “It’s a Family Reunion,” and the performance and entertainment – including a gospel celebration – on multiple stages will be dedicated to the musicians of New Orleans. 10 a.m. to 7 p.m., West 135th Street from Fifth Avenue to St. Nicholas Avenue; free.